U.S. Pat. No. 8,242,746 discloses a circuit arrangement for measuring the cell voltages of individual cells of an accumulator pack. The individual cells form a cell grouping composed of a series circuit of individual cells, wherein potential points are formed between electrically adjacent individual cells of the series circuit. The potentials of the potential points which follow one another in the series circuit increase in absolute value from a reference potential. Each potential point of the series circuit is connected to a measuring input of an evaluation device via a measuring resistor and a switch. At the measuring resistor, a voltage drops after the closing of the switch and is registered by the evaluation device. The measuring resistors which are assigned to a potential point are connected in series in the manner of a resistor cascade and form an ohmic load of the individual cells to be measured. In this context, when the first individual cell of the series circuit is measured, the closed switch and the first measuring resistor form, with the first individual cell, a first electrical measuring circuit. If the second switch is closed—or all the other switches are open—the first individual cell, the second individual cell, the first measuring resistor and the second measuring resistor form a closed measuring circuit. An individual cell is electrically loaded with each measurement, wherein the loading of the first individual cells of a series circuit is greater than that of the last individual cells of the series circuit. The individual cells are respectively measured by closing the individual switches, wherein in each case the voltage which drops at the measuring resistor is registered and evaluated.
The expenditure involved with such a circuit arrangement for measuring individual voltages is high; since the measuring voltages are registered under ohmic load, the individual cells are subject to heavy electrical loading, which can influence the service life of the accumulator pack.